No exploitation reportedFix available

CVE-2026-83540

Q: Is CVE-2026-83540 actively exploited?

Active exploitation of CVE-2026-83540 has not been confirmed. Its EPSS score was 0.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-83540?

CVE-2026-83540 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

wolfSSHd on Windows race condition leading to logon token reused across connections

No exploitation reported by the sources we read.

Published2026-10-07
Fixed in1.6.0
WeaknessCWE-287 · CWE-613

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

When password or public key authentication is used with the Windows port of wolfSSHd, the Windows logon token acquired for one authenticated connection is not released before a token is acquired for a subsequent connection, resulting in user login poisoning between connections. A less privileged user with a valid account on the server can exploit this to force a login as a more privileged user. The vulnerability was introduced with the initial Windows port of wolfSSHd in wolfSSH version 1.4.15 and affects all versions through 1.5.0. Non-Windows builds of wolfSSHd are not affected.

Timeline

dates in UTC

2026-10-0703:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-83540?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-83540?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Wolfssh

Branch	Affected	Fixed in	Source
1.x	≥ 1.4.15, < 1.6.0	1.6.0	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Wolfssh to 1.6.0

Advisories and patches

github.comPatch
github.comPatch
www.wolfssl.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2026-10-07
OpenCVESSVC decisionnone—
CNACVSS 4.07.7read 2026-10-23
NVDCVSS 3.18.8read 2026-10-23
CNAweakness (CWE)CWE-287, CWE-613read 2026-10-23
FIRST EPSSEPSS score0.4 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 4.0 vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Published: 2026-10-07
Last Modified: 2026-10-13
NVD status: Analyzed

Frequently asked questions

What is CVE-2026-83540?

Is CVE-2026-83540 actively exploited?

Active exploitation of CVE-2026-83540 has not been confirmed. Its EPSS score was 0.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-83540?

CVE-2026-83540 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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